The instant invention relates to a sub-roof with roofing boards for covered roofs.
To build up a sub-roof, an insulating board is disclosed in DE-GM 1,932,832 which hangs by an upper projection on a roof lath, whereby the upper portion of an insulating board which is already installed nearer to the eaves is partially overlapped. A crosspiece extends along the lower area of each insulating board for the engaging of the projections of roof tiles. The crosspieces are cut by water channels. An overlapping profile is attached to the lateral edges of the insulating boards to render the lateral abutments water-tight.
A sub-roof construction with the above insulating board has a disadvantage in that damages are often inflicted upon the insulating boards as early as during open construction work, e.g. breaking away of the relatively thin, overlapping lateral parts, and this leads to low-temperature bridges and to the loss of water-tightness in the sub-roof. This roof construction is practical only with relatively thin insulating boards, but with the greater insulating thicknesses in demand today, roofing of such an overall insulating layer thickness leads to a step-like surface with high steps, depending upon the thickness of the insulating boards, so that a desired uniform overall thickness of the insulation, especially in the areas of overlaps, is out the question. A further disadvantage results from the fact that when the thicker insulating layers are used, the individual insulating boards tip away from the roof when they are laid on steeper roofs, especially when the roofing tiles are hooked in. With flat roofs on the other hand, the problem arises that when thicker insulating layers are used, the insulating boards are placed in a nearly horizontal position because of the overlaps, so that water may back up and the watertightness of the roof is then no longer ensured. The lack of wind tightness is a further disadvantage, as transverse overlap is minimal.
A further, known embodiment of insulating boards used to built up a sub-roof is disclosed in DE-PS 2349 710. These boards are engaged over their entire width, as seen vertically to the eaves, between the roof battens and their lateral surface on the eaves side is supported by the ridge-side lateral surface of the roof batten below. Stepped mortises are provided in the area of cross-overlap so that an essentially planar upper and lower surface of the sub-roof is created. The disadvantage of this design is the great fragility of the profiled lateral edges, which may have, as a consequence, that the sub-roof is no longer tight and no longer insulates in areas where it has been damaged. When thicker insulating boards are used, there is the further danger that these may tip out of the roof surface after or during installation of the roof tiles. For the drainage of the sub-roof, a water guiding groove must be installed at the lowest point of the stepped mortises, leading from there at an upward slant to the insulating board below. With thicker boards and flatter roof surfaces these water guiding grooves are slanted ever more horizontally, so that water may back up. Tightness against water and wind must, on the whole, be ensured by complicated, easily damaged and overlapping configurations at the edges. Storm-proofing, e.g. roofing with insulating board as a provisional measure, is only possible with the help of expensive additional means.
It is, however, a particular disadvantage of the known boards that insulating boards of different dimensions must be used with different batten intervals. It is known that batten intervals are different for different roof tile products and measure, for example, 32 to 36 cm for roof pan covers. It is, therefore, necessary to manufacture boards in narrow gradations within that range, to keep them in stock, to take them into consideration in planning, and to order them, all of which is expensive. Left-overs in the hands of artisans and roofers are difficult to distinguish from each other, are difficult to store, and thus to use up. Because of the complicated configuration of the edges, cut-off ends, or partially cut, insulating boards can hardly ever be used again, so that much waste is produced in cutting.
Insulating boards, which are wider than the given batten interval, cannot be used. If insulating boards are used which are too narrow for the batten, interval gaps occur and, as a result, weak spots in the insulation are thus created in the area of stepped mortise overlap.